Whether hybridization plays a positive or negative role in speciation remains a controversial issue to date. Genetic factors have been widely studied, but ecological factors also play an important role. Although studies on the ecological adaptation of hybrids between different niche parents have been widely reported, cases of extreme niche parental hybridization have not been documented, which may show more ecological phenomena in the fields of hybrid speciation and ecological species isolation.
Taking Cyprinidae fish parents (Schizothorax wangchiachii and Percocypris pingi) with extreme ecological niches (herbivorous and carnivorous) and their F1 hybrids as research objects, fish, shrimp, blood worms and periphytic algae were selected as food correspond to four different ecological niches. Morphologically, most external and skeletal traits in the F1 hybrids were balanced between the parents, but digestive traits were closer to those of herbivorous parents. In terms of diet, the F1 hybrids weakly foraged for parental food resources, but can more effectively forage for intermediate food resources. In foraging abilities, the F1 hybrids showed low foraging enthusiasm and abilities for parent resources, although the former was the more important factor. Interestingly, the F1 hybrids showed high foraging enthusiasm and success rates when they first foraged for fish, but then they vomited fish debris as a result of mechanical difficulty in chewing rather than taste, and the reason was a contradiction between the genetic behaviours and intermediate morphology. This behaviour was harmful and was persistent in some individuals, representing a new mechanism in ecological species isolation. However, the F1 hybrids have also shown evidence of new ecological niche formation in favour of hybrid speciation by abandoning foraging parent resources and focusing more on foraging intermediate foods.
(1) Low foraging enthusiasm is an important reason for the fitness decrease of F1 hybrids to parent food. (2) The contradiction between genetic behavior and intermediate traits is reported for the first time. (3) F1 hybrids may form an intermediate ecological niche between parents proved experimentally.